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What Are the Different Types of ROM (Read Only Memory)?


Read-only memory (ROM)

Read-only memory (ROM), is a type of electronic storage built into the device during production. You will find ROM (read-only memory) chips in computers and many other types of electronic products VCRs game consoles and car radios all use ROM to complete their functions smoothly. 


ROM chips come built into an external unit – like flash drives and other auxiliary memory devices – or are installed in the device hardware on a removable chip. 

Non-volatile memory like ROM remains viable even without power.


Let’s Discuss the Different Types of Rom (Read-Only Memory) and Their Characteristics

MROM (Masked ROM)

The first ROMs were wired devices that contained a pre-programmed data set or instructions. This type of ROM is known as masked ROMs which are inexpensive.


PROM (Programmable Read-Only Memory)

PROM is a read-only memory that can only be changed once by a user. The user buys a blank PROM and feeds the desired content through a PROM program. 

Inside the PROM chip, there are small fuses that burn during programming. It can be programmed only once and cannot be deleted.


EPROM (Erasable and Programmable Read-Only Memory)

EPROM can be erased by exposing it to ultraviolet light for up to 40 minutes. Typically an EPROM delete achieves this function. During programming, an electric charge was captured in an insulated gate area. 


The charge has been stored for more than 10 years because the charge has no leakage path. To erase this charge ultraviolet light is transmitted through a quartz crystal window (lid). 

This exposure to purple light dissipates the charge. In normal use, the quartz lid is sealed with a sticker.


EEPROM (Electrically Erasable and Programmable Read-Only Memory)

EEPROM is electrically programmed and deleted. It can be deleted and reprogrammed about ten thousand times. Both deletion and programming take about 4 to 10 milliseconds (the millisecond). 

In EEPROM you can selectively delete and program any location. You can delete the EEPROM types one by one at a time and not delete the entire chip. Hence the reprogramming process is flexible but slow.